Effects of luting agent and thermocycling on bond strengths to root canal dentine

Aim To investigate the effects of luting agent and thermocycling on bond strengths to root canal dentine. Methodology Extracted maxillary canines (n =144) were root filled and divided into six groups of 24 teeth each. Fibre posts (FRC Postec) were inserted using six luting agents: Panavia F, Multilink, Variolink II, PermaFlo DC, RelyX Unicem and Clearfil Core. Each root was sliced into six discs (thickness 1 mm) representing the coronal, middle and apical part of the root canal. Push-out tests were performed 24 h after post insertion (n = 12) as well as after thermocycling (5000x; 5-55 degrees C, 30 s) (n = 12). Statistical analysis was conducted using analysis of variance (ANOVA) followed by post-hoc comparisons (Tukey-B). The influence of thermocycling on bond strengths was investigated for each material and region separately using t-tests. Results The bond strengths were significantly affected by the luting agent (P < 0.001), the root position (P = 0.003) and thermocycling (P < 0.001; three-way ANOVA). RelyX had significantly higher bond strengths compared with all other materials (P < 0.05; Tukey-B). The apical region of the root canal had significantly higher bond strengths compared with the middle and coronal region (P < 0.05; Tukey-B). After thermocycling for RelyX a significant increase in bond strengths was detected for the middle and apical region (P < 0.01; t-test, Bonferroni factor 18). Conclusions Bond strengths were affected significantly by luting agent and root position. RelyX had higher bond strengths compared with other materials. The apical region of the canals was characterized by significantly higher bond strengths.